Are you aware of various layer of OSI model? The biggest advantage of layering approach is Independence. If we have to make some changes on one layer, others will be unaffected. Data independence is the capacity to change the schema at one level without having the change at other higher level. There are two types of data independence:

Logical Data Independence: Change of conceptual schema without having any change in application program

Physical Data Independence: Change in storage mechanism without affecting the logical schema.